Conventionally, in a molding machine; for example, an injection molding machine, resin is melted within a heating cylinder through application of heat; the thus-molten resin is charged into a cavity of a molding apparatus; and the resin within the cavity is cooled to set, thereby yielding a molded article.
The injection molding machine has a molding apparatus, which serves as a resin molding apparatus; a mold-clamping apparatus; and an injection apparatus. The injection apparatus includes a heating cylinder for melting resin through application of heat; an injection nozzle attached to the front end of the heating cylinder and adapted to inject the molten resin; and a screw disposed within the heating cylinder rotatably and in a manner capable of advancing and retreating. The molding apparatus includes a stationary mold and a movable mold. The mold-clamping apparatus advances and retreats the movable mold, whereby the molding apparatus performs mold closing, mold clamping, and mold opening. When mold clamping is performed, a cavity is formed between the stationary mold and the movable mold.
In a metering step, when the screw is rotated, the resin fed into the heating cylinder is melted and stored ahead of the screw. In the course of this operation, the screw is retreated. In this period, the molding apparatus performs mold closing and mold clamping. Subsequently, in an injection step, the screw is advanced, whereby the resin stored ahead of the screw is ejected from the injection nozzle and is charged into the cavity. Next, in a cooling step, the resin within the cavity is cooled to set. Subsequently, mold opening is performed, and the molded article is ejected.
FIG. 1 is a sectional view of a conventional molding apparatus.
In FIG. 1, reference numeral 11 denotes a molding apparatus for molding an article, such as a light guide plate; reference numeral 12 denotes a stationary mold; and reference numeral 13 denotes a movable mold disposed in a manner capable of advancing and retreating in relation to the stationary mold 12. By means of an unillustrated mold-clamping apparatus, the movable mold 13 is advanced; i.e., mold closing is performed; the movable mold 13 is brought into contact with the stationary mold 12; i.e., mold clamping is performed, thereby forming cavities C1, C2, each having a rectangular shape, between the stationary mold 12 and the movable mold 13; and the movable mold 13 is retreated from the stationary mold 12; i.e., mold opening is performed.
Reference numeral 15 denotes a sprue formed in the stationary mold 12. Communication is established between the tip end of the sprue 15 and the cavities C1, C2 through gates g1, g2, respectively.
The movable mold 13 includes an upper plate 21 and a lower plate 22, which supports the upper plate 21. A transfer plate 34 is attached to a surface of the movable mold 13 which is located within the cavities C1, C2 and faces the stationary mold 12. The transfer plate 34 has a transfer surface which faces the stationary mold 12 and on which fine pits and projections are formed in a predetermined pattern. Temperature-regulating channels 23 are formed in the lower plate 22. A temperature-regulating medium is run through the temperature-regulating channels 23 so as cool the molding apparatus 11 and resin within the cavities C1, C2.
An unillustrated injection apparatus is disposed in a manner capable of advancing and retreating in relation to the molding apparatus 11. An injection nozzle of the injection apparatus is pressed against the stationary mold 12 of the molding apparatus 11 in a mold-clamped state, and resin is ejected from the injection nozzle. The ejected resin is charged into the cavities C1, C2 through the gates g1, g2, respectively.
The resin in the cavities C1, C2 is cooled, by the temperature-regulating medium, to set. At this time, the pattern of the transfer surface of the transfer plate 34 is transferred onto the resin. Subsequently, mold opening is performed, thereby yielding a light guide plate (refer to, for example, Patent Document 1).
Patent Document 1: Japanese Patent Application Laid-Open (kokai) No. 2000-249538